1. Field of the Invention
This invention relates generally to systems for endurance testing aircraft propulsion system gear boxes and, more particularly, to a torque applier for simulating torque transfer through the gear box.
2. Description of the Prior Art
In a recently proposed aircraft propulsion system, a turboshaft gas turbine engine in the 10,000 horsepower (Hp) category is mounted on the airframe and drives counter-rotating bladed elements, sometimes referred to as propfans or unducted fans, through a planetary differential gear box which divides the engine power between the bladed elements. The gear box has oppositely rotating, coaxial output shafts connected to the bladed members and to two elements of a high capacity planetary differential within the gear box. The gear box also has an input shaft aligned on the same axis as the output shafts and connected to the turbine engine and to the third element of the planetary differential. Preproduction endurance testing of such gear boxes in controlled environments can be performed by placing the gear box between a power source capable of developing high torque corresponding to rated engine power at rated input shaft speeds of about 10,000 RPM and a power absorption device capable of dissipating rated power. Another known approach is to rotate the input shaft at rated speed while simulating rated gear tooth and bearing loads through a recirculating torque system including the test transmission, a slave transmission of like speed and torque ratio having its output shafts connected to the output shafts of the test transmission, and a rotary actuator between the input shafts of the test and slave transmissions capable of applying opposite torsional moments to the input shafts as they rotate. However, the coaxial and colinear arrangement of the input and output shafts, together with the mechanical considerations associated with simulating 10,000 Hp powerflow at input shaft speeds in excess of 10,000 RPM, represents a significant engineering challenge. A torque applier according to this invention, in a torque recirculation test environment, uses a relatively low power prime mover to rotate the test gear box planetary differential at rated speeds and also uses commercially available rotary actuators of relatively low capacity, all in a simple and compact structure.